Torque-limiting spindle

ABSTRACT

An exemplary torque-limiting spindle includes an input member, an output member, a clutch mechanism, and a bias mechanism. The input member extends along a longitudinal axis, is configured for connection with a handle, and includes a first engagement feature. The output member extends along the longitudinal axis, is configured for connection with a rotatable member of a lockset, and includes a second engagement feature. The clutch mechanism includes the first engagement feature and the second engagement feature. The bias mechanism is engaged with the input member and the output member and exerts a biasing force urging the first engagement feature and the second engagement feature into engagement with one another.

TECHNICAL FIELD

The present disclosure generally relates to locksets, and moreparticularly but not exclusively relates to systems and methods forlimiting a torque input to a lockset.

BACKGROUND

Certain locksets include a handle that is operable to retract a boltwhen the lockset is in an unlocked condition, and which cannot retractthe bolt when the lockset is in a locked condition. In such locksets, itis common to lock the handle in position when the lockset is in thelocked condition, thereby preventing the handle from retracting thebolt. However, such locksets can be susceptible to an over-torqueingattack, in which an excessive torque is applied to the handle. Suchexcessive torques can damage the handle and/or the internal componentsof the lockset. As such, certain locksets include a mechanism thatprevents excessive torques from being transmitted from the handle to theinternal components of the lockset, such as a frangible element or aslip clutch. However, existing forms of such torque-limiting mechanismssuffer from certain drawbacks or limitations. For example, frangibleelements must be replaced after being broken, and existing slip clutchesare typically complex and require several parts, such as rollers thatcan be lost if the slip clutch is opened. Moreover, traditional slipclutches, upon slipping, provide the handle with a new home orientation,and it may be difficult to return the handle to its desired homeorientation. For these reasons among others, there remains a need forfurther improvements in this technological field.

SUMMARY

An exemplary torque-limiting spindle includes an input member, an outputmember, a clutch mechanism, and a bias mechanism. The input memberextends along a longitudinal axis, is configured for connection with ahandle, and includes a first engagement feature. The output memberextends along the longitudinal axis, is configured for connection with arotatable member of a lockset, and includes a second engagement feature.The clutch mechanism includes the first engagement feature and thesecond engagement feature. The bias mechanism is engaged with the inputmember and the output member and exerts a biasing force urging the firstengagement feature and the second engagement feature into engagementwith one another. Further embodiments, forms, features, and aspects ofthe present application shall become apparent from the description andfigures provided herewith.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a partially-exploded assembly view of a lockset according tocertain embodiments.

FIG. 2 is a plan view of a chassis assembly of the lockset illustratedin FIG. 1 .

FIG. 3 is a perspective illustration of a torque-limiting spindleaccording to certain embodiments.

FIG. 4 is a partial cutaway view of the torque-limiting spindleillustrated in FIG. 3 .

FIG. 5 is a perspective view of an input member of the torque-limitingspindle illustrated in FIG. 3 .

FIG. 6 is a perspective view of an output member of the torque-limitingspindle illustrated in FIG. 3 .

FIG. 7 is a partial cutaway view of the torque-limiting spindleillustrated in FIG. 3 .

FIG. 8 is a proximal end view of the torque-limiting spindle illustratedin FIG. 3 .

FIG. 9 is a partial cutaway view of a torque-limiting spindle accordingto certain embodiments.

FIG. 10 is a cross-sectional illustration of a torque-limiting spindleaccording to certain embodiments.

FIG. 11 is a cross-sectional illustration of a torque-limiting spindleaccording to certain embodiments.

FIG. 12 is an end view of the torque-limiting spindle illustrated inFIG. 11 .

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Although the concepts of the present disclosure are susceptible tovarious modifications and alternative forms, specific embodiments havebeen shown by way of example in the drawings and will be describedherein in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,”“an illustrative embodiment,” etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may or may not necessarily includethat particular feature, structure, or characteristic. Moreover, suchphrases are not necessarily referring to the same embodiment. It shouldfurther be appreciated that although reference to a “preferred”component or feature may indicate the desirability of a particularcomponent or feature with respect to an embodiment, the disclosure isnot so limiting with respect to other embodiments, which may omit such acomponent or feature. Further, when a particular feature, structure, orcharacteristic is described in connection with an embodiment, it issubmitted that it is within the knowledge of one skilled in the art toimplement such feature, structure, or characteristic in connection withother embodiments whether or not explicitly described.

As used herein, the terms “longitudinal,” “lateral,” and “transverse”are used to denote motion or spacing along three mutually perpendicularaxes, wherein each of the axes defines two opposite directions. In thecoordinate system illustrated in FIG. 1 , the X-axis defines first andsecond longitudinal directions, the Y-axis defines first and secondlateral directions, and the Z-axis defines first and second transversedirections. These terms are used for ease and convenience ofdescription, and are without regard to the orientation of the systemwith respect to the environment. For example, descriptions thatreference a longitudinal direction may be equally applicable to avertical direction, a horizontal direction, or an off-axis orientationwith respect to the environment.

Furthermore, motion or spacing along a direction defined by one of theaxes need not preclude motion or spacing along a direction defined byanother of the axes. For example, elements that are described as being“laterally offset” from one another may also be offset in thelongitudinal and/or transverse directions, or may be aligned in thelongitudinal and/or transverse directions. The terms are therefore notto be construed as limiting the scope of the subject matter describedherein to any particular arrangement unless specified to the contrary.

Additionally, it should be appreciated that items included in a list inthe form of “at least one of A, B, and C” can mean (A); (B); (C); (A andB); (B and C); (A and C); or (A, B, and C). Similarly, items listed inthe form of “at least one of A, B, or C” can mean (A); (B); (C); (A andB); (B and C); (A and C); or (A, B, and C). Items listed in the form of“A, B, and/or C” can also mean (A); (B); (C); (A and B); (B and C); (Aand C); or (A, B, and C). Further, with respect to the claims, the useof words and phrases such as “a,” “an,” “at least one,” and/or “at leastone portion” should not be interpreted so as to be limiting to only onesuch element unless specifically stated to the contrary, and the use ofphrases such as “at least a portion” and/or “a portion” should beinterpreted as encompassing both embodiments including only a portion ofsuch element and embodiments including the entirety of such elementunless specifically stated to the contrary.

In the drawings, some structural or method features may be shown incertain specific arrangements and/or orderings. However, it should beappreciated that such specific arrangements and/or orderings may notnecessarily be required. Rather, in some embodiments, such features maybe arranged in a different manner and/or order than shown in theillustrative figures unless indicated to the contrary. Additionally, theinclusion of a structural or method feature in a particular figure isnot meant to imply that such feature is required in all embodiments and,in some embodiments, may be omitted or may be combined with otherfeatures.

With reference to FIG. 1 , illustrated therein is a lockset 100according to certain embodiments. The lockset 100 generally includes ahandle 110, a chassis assembly 200 configured for mounting in a door,and a torque-limiting spindle 300 according to certain embodiments. Asdescribed herein, the chassis assembly 200 includes a latchbolt 220 anda rotatable member in the form of a hub 230 connected with the latchbolt220 such that rotation of the hub 230 retracts the latchbolt 220, andthe spindle 300 is connected between the handle 110 and the hub 230 toselectively transmit torque from the handle 110 to the hub 230. Whilethe illustrated lockset 100 is provided in the form of a mortiselockset, it is also contemplated that the spindle 300 described hereinmay be utilized in connection with other forms of locksets and/orhandlesets, such as cylindrical format locksets, tubular formatlocksets, and escutcheon format handlesets (e.g., exit device trims).

The illustrated handle 110 generally includes a shank 112 that extendsalong a longitudinal axis 102 and a lever portion 114 that extends in atleast one direction transverse to the longitudinal axis 102. The shank112 includes a cavity 113 operable to receive a input member 310 of thespindle 300 for rotational coupling with the input member 310. While theillustrated handle 110 is provided as a lever handle, it is alsocontemplated that the handle 110 may be provided as a knob handle oranother form of manual actuator, such as a thumbturn.

With additional reference to FIG. 2 , the chassis assembly 200 generallyincludes a case 210, a latchbolt 220 movably mounted in the case 210 formovement between an extended position and a retracted position, a hub230 rotatably mounted in the case 210, a retractor 240 configured toretract the latchbolt 220 in response to rotation of the hub 230 from ahome position, a catch 250 operable to selectively prevent rotation ofthe hub 230 from the home position, and a drive assembly 260 operable tomove the catch 250 between a locking position and an unlocking position.

The case 210 is configured for mounting in a door, and in theillustrated form is configured for mounting in a mortise of a door. Thecase 210 generally includes a housing 212 and a cover plate 214removably coupled to the housing 212 to enclose the internal componentsof the chassis assembly 200 within the case 210.

The latchbolt 220 is mounted within the case 210 for movement between anextended position and a retracted position, and generally includes alatchbolt head 222 and a tail 224 extending rearward from the head 222.A biasing member such as a spring 226 is engaged with the latchbolt 220and biases the latchbolt 220 toward its extended position. As describedherein, the tail 224 is engaged with the retractor 240 such that theretractor 240 is operable to retract the latchbolt 220 in response torotation of the hub 230 from its home position.

The hub 230 is rotatably mounted in the case 210 for rotation about thelongitudinal axis 102, and generally includes a body portion 232defining an opening 233 and an arm 234 projecting from the body portion232 in a first direction, and in the illustrated form further includes aprojection 236 projecting from the body portion 232 in a seconddirection different from the first direction. The opening 233 isoperable to receive an output member 320 of the spindle 300 forrotational coupling with the output member 320. While the illustratedopening 233 has a generally square-shaped geometry, it is alsocontemplated that other geometries may be utilized. As described herein,the arm 234 is operable to engage the retractor 240 for retraction ofthe latchbolt 220, and the projection 236 is operable to engage thecatch 250 to selectively lock the hub 230. It should be appreciated thata second hub may be positioned on an opposite side of the retractor 240as the illustrated hub 230 for engagement with a second handle via asecond spindle.

The retractor 240 is pivotably mounted in the case 210 and is engagedwith the latchbolt tail 224. The retractor 240 includes alongitudinally-projecting post 242 operable to engage the arm 234 of thehub 230. During rotation of the hub 230 from its illustrated homeposition in an actuating direction (clockwise in FIG. 2 ), the arm 234engages the post 242 and pivots the retractor 240 in a correspondingactuating direction, thereby causing the retractor 240 to retract thelatchbolt 220. In embodiments in which the chassis 200 includes a secondhub opposite the hub 230, rotation of the second hub may similarlyactuate the retractor 240 for retraction of the latchbolt 220.

The catch 250 is movably mounted in the case 210 for lateral movementbetween a locking position and an unlocking position, and in theillustrated form includes a recess 252 operable to receive theprojection 236, and a cam slot 254 operable to engage the drive assembly260. When the catch 250 is in its locking position, the projection 236is received in the recess 252 such that the catch 250 prevents rotationof the hub 230 from its home position. When the catch 250 is movedtoward its unlocking position (to the right in FIG. 2 ), the recess 252moves away from the projection 236, thereby permitting rotation of thehub 230. In the illustrated form, the hub 230 includes a projection 236,and the catch 250 includes a recess 252 operable to receive theprojection 236. It is also contemplated that other configurations may beutilized in order for the catch 250 to selectively lock the hub 230against rotation. For example, the catch 250 may include a projection,and the hub 230 may include a recess that receives the catch projectionwhen the catch 250 is in its locking position.

The drive assembly 260 is engaged with the catch 250 and is operable tomove the catch 250 between its locking position and its unlockingposition. The drive assembly 260 generally includes a link 262 mountedfor movement between a first transverse position and a second transverseposition to laterally drive the catch 250 between its locking positionand its unlocking position. More particularly, a projection such as apin 263 extends into the cam slot 254 such that engagement between thecam slot 254 and the pin 263 causes the catch 250 to move laterallybetween its locking position and its unlocking position in response totransverse movement of the link 262 between its first position and itssecond position.

In the illustrated form, the drive assembly 260 further includes anelectromechanical driver 264 and a transmission 266 engaged between thedriver 264 and the link 262 such that the driver 264 is operable to movethe link 262 between its first and second positions. Additionally oralternatively, the drive assembly 260 may include mechanical featuresfor driving the link 262 between its first position and its second.While other configurations are contemplated, in the illustrated form,the driver 264 is provided as a rotary motor having a threaded outputshaft 265, and the transmission 266 includes a spring 267 and a threadedcoupler 268. One end of the spring 267 is engaged with the link 262, andthe other end of the spring 267 is engaged with the shaft 265 via thecoupler 268.

Rotation of the shaft 265 in a first rotational direction drives thecoupler 268 in a first transverse direction, thereby causing the spring267 to exert a corresponding transverse force on the link 262. Thisforce drives the link 262 from its first position toward its secondposition, thereby moving the catch 250 from its locking position to itsunlocking position. Conversely, rotation of the shaft 265 in a secondrotational direction opposite the first rotational direction drives thecoupler 268 in a second transverse direction opposite the firsttransverse direction, thereby causing the spring 267 to exert acorresponding transverse force on the link 262. This force drives thelink 262 from its second position toward its first position, therebymoving the catch 250 from its unlocking position to its lockingposition.

It should be appreciated that the illustrated arrangement of the driveassembly 260 is intended as an example only, and that otherconfigurations are contemplated. As one example, the spring 268 may berotationally coupled with the shaft 265, and coils of the spring 268 maybe engaged with the link 262 such that rotation of the spring 268 inopposite rotational directions urges the link 262 in opposite transversedirections. As another example, the motor may be replaced with asolenoid or another form of linear actuator that drives the link 262between its first and second positions. As a further example, theelectromechanical driver 264 may be omitted, and movement of the link262 may be accomplished mechanically, for example by turning a thumbturnof the lockset 100 and/or a key associated with the lockset 100.

With additional reference to FIGS. 3 and 4 , the torque-limiting spindle300 generally includes a proximal input member 310, a distal outputmember 320, a clutch mechanism 330 defined by the input member 310 andthe output member 320, and an internal bias mechanism 350 biasing theinput member 310 and the output member 320 into contact with oneanother, and may further include one or more stop features 360. Asdescribed herein, the input member 310 is configured for connection withthe handle 110, the output member 320 is configured for connection withthe hub 230, the clutch mechanism 330 is configured to limit torquetransmission between the input member 310 and the output member 320 to athreshold torque, the bias mechanism 350 generates a biasing forcecorresponding to the threshold torque, and the stop feature(s) 360 aidin retaining the bias mechanism 350 within the spindle 300.

With additional reference to FIG. 5 , the input member 310 extends alongthe longitudinal axis 102 and includes a body portion 312 sized andshaped to be received in the cavity 113 of the shank 112, and a distalend portion 314 that defines a first engagement feature 331 of theclutch mechanism 330. A chamber 316 extends at least partially throughthe input member 310 and is defined in part by a distal shoulder 317. Inthe illustrated form, the chamber 316 extends to an open proximal end318 of the input member 310. As described herein, the bias mechanism 350is partially seated in the chamber 316, and engages the shoulder 317 todistally urge the input member 310 into engagement with the outputmember 320.

With additional reference to FIG. 6 , the output member 320 extendsalong the longitudinal axis 102 and includes a body portion 322 sizedand shaped to be received in the opening 233 of the hub 230 and aproximal end portion 324 that defines a second engagement feature 335 ofthe clutch mechanism 330. In the illustrated form, a threaded bore 326is formed in the output member 320 and receives a distal end portion ofa bolt 354 of the bias mechanism 350. It is also contemplated that thebore 326 may not necessarily be threaded. The output member 320 mayfurther include a flange 328, and a spring may be positioned between theshank 112 and the flange 328 to bias the body portion 322 into the hubopening 233, thereby accommodating for different thicknesses of the doorpanel to which the lockset 100 is installed.

The clutch mechanism 330 includes a first engagement feature 331 definedby the distal end portion 314 of the input member 310 and a secondengagement feature 335 defined by the proximal end portion 325 of theoutput member 320. As described herein, the engagement features 331, 335are biased into engagement with one another by the bias mechanism 350.Each of the illustrated engagement features 331, 335 is provided as awave-like engagement feature including a plurality of ramps that defineat least one projection and at least one recess. For example, theillustrated first engagement feature 331 includes a plurality of firstramps 332 that at least partially define a plurality of firstprojections 333 and a plurality of first recesses 334 positioned betweenthe first projections 333. Similarly, the illustrated second engagementfeature 335 includes a plurality of second ramps 336 that at leastpartially define a plurality of second projections 337 and a pluralityof second recesses 338 positioned between the second projections 337.The ramps 332, 336 are shaped to generally conform to one another suchthat the first projections 333 are received within the second recesses338 and the first recesses 334 receive the second projections 337.

With additional reference to FIG. 7 , the illustrated internal biasmechanism 350 is mounted within the input member 310 and the outputmember 320, and generally includes a spring 352 and a bolt 354 to whichthe spring 352 is mounted. The bolt 354 includes an elongated body 355,a proximal head 356, and a distal threaded portion 358. The bolt 354 isprimarily positioned in the chamber 316 of the input member 310, and thedistal threaded portion 358 is threaded into the threaded bore 326 ofthe output member 320 to provide the bolt 354 with a fixed longitudinalposition relative to the output member 320. It is also contemplated thatthe distal portion 358 may not necessarily be threaded, and may insteadbe engaged with the output member 320 in another manner, such as via afastener and/or adhesive. As described herein, however, the threadedengagement between the bolt 354 and the output member 320 may facilitateadjustment of the preloading of the spring 352 to thereby adjust thethreshold torque that the spindle 300 is capable of transmitting. Thebolt body 355 extends through the spring 352 such that the spring 352 iscaptured between the head 356 and the shoulder 317. As a result, thespring 352 distally biases the input member 310 into contact with theoutput member 320.

As described herein, the threshold torque that the spindle 300 iscapable of transmitting between the input member 310 and the outputmember 320 (and thus from the handle 110 to the hub 230) corresponds tothe biasing force exerted by the bias mechanism 350. In certainembodiments, the spring 352 may be preloaded to increase the biasingforce exerted by the bias mechanism 350. Additionally or alternatively,the bolt head 356 may include a feature by which the head 356 can beengaged by a tool operable to tighten or loosen the bolt 354 to increaseor decrease the preload of the spring 352. For example, the illustratedhead 356 includes a tool-engaging feature 357 in the form of a recesssized and shaped to receive a tip of a hex key by which the bolt 354 canbe rotated. It is also contemplated that the tool-engaging feature 357may take another form, such as that of a Phillips head recess, aflathead recess, a star-drive recess, or a recess or projection ofanother geometry by which torque can be transmitted from an appropriatetool to the bolt 354. In the illustrated form, such a tool may beinserted through the open proximal end 318 to facilitate adjustment ofthe preload provided by the spring 352.

With additional reference to FIG. 8 , the stop feature(s) 360 areconfigured to prevent exiting of the bias mechanism 350 from the cavity316 via the open proximal end 318 of the input member 310. In theillustrated form, the stop feature(s) 360 are provided in the form of apair of radial projections 362 that project inwardly to reduce theeffective diameter of the open proximal end 318. More particularly, theillustrated stop feature(s) 360 reduce the effective diameter of theopen proximal end 318 to an effective diameter that is less than thediameter of the bolt head 356. As a result, the bias mechanism 350remains captured within the chamber 316, even when the threaded distalportion 358 is fully disengaged from the threaded bore 326.

Should the spring 352 be preloaded as described above, it may be thecase that loosening the bolt 354 until the distal end 358 exits thethreaded bore 326 causes the spring 352 to continue urging the bolt 354in the proximal direction. Should the preload be sufficiently high, thespring 352 may exert a sufficient force to cause the bolt 354 to shootin the proximal direction toward the user when the threads of the distalend 358 disengage from the threads of the bore 326. However, the exitingof the bolt 354 from the cavity 316 by the stop feature(s) 360 isprevented as described above, thereby protecting the user from harm.

During manufacture and/or assembly of the spindle 300, the stopfeature(s) 360 may initially be omitted from the input member 310 tofacilitate insertion of the bias mechanism 350 into the chamber 316. Thebias mechanism 350 may be inserted into the chamber 316 such that thethreaded distal end portion 358 projects beyond the distal end of theinput member 310. The threaded distal end portion 358 may then beinserted into the threaded bore 326, and an appropriate tool may beinserted via the open proximal end 318 to rotate the bolt 354 until adesired preloading of the spring 352 is achieved. The stop feature(s)360 may then be formed in the input member 310, for example by deformingthe proximal end of the input member 310 to define the radialprojections 362. It is also contemplated that the stop member(s) 360 maybe provided to the input member 310 in another manner, for example byinserting a set screw through an opening formed in the proximal endportion of the input member 310.

Once assembled, the spindle 300 may be installed to the lockset 100 in amanner similar to that of conventional spindles. For example, the distalend portion of the spindle 300, which is defined by the body portion 322of the output member 320, may be inserted into the hub opening 233 forengagement with the hub 230 in a manner common to mortise locksets.Similarly, the proximal end portion of the spindle 300, which is definedby the body portion 312 of the input member 310, may be inserted intothe handle cavity 113 for engagement with the handle 110. The inputmember 310 may, for example, include a radial bore operable to receive aset screw by which the handle 110 may be longitudinally and rotationallycoupled with the input member 310.

Once installed to the lockset 100, the spindle 300 serves to selectivelytransmit torque from the handle 110 to the hub 230 by transmittingtorques below a threshold torque while slipping in response toapplication of torque in excess of the threshold torque. The thresholdtorque is sufficiently high that when the lockset 100 is in its unlockedstate, the spindle 300 is capable of transmitting a torque sufficient torotate the hub 230 to drive the latchbolt 220 to its retracted position.More particularly, the bias mechanism 350 retains the engagementfeatures 331, 335 in engagement with one another such that torquesapplied to the handle 110 are transmitted to the hub 230 for retractionof the latchbolt 220.

When the lockset 100 is in its locked state and a torque below thethreshold torque value is applied to the handle 110, the bias mechanism350 retains the engagement features 331, 335 in engagement with oneanother such that the ramps 332, 336 resist relative rotation of theinput member 310 and the output member 320. As the applied torqueincreases, the engagement features 331, 335 begin to slip, and the ramps332, 336 drive the input member 310 axially away from the output member320, thereby permitting rotation of the input member 310 relative to theoutput member 320 and preventing the excessive torque from beingtransmitted to the hub 230. Should the excessive torque continue to beapplied, each protrusion 333 will enter the recess 336 that waspreviously adjacent to the protrusion, thereby providing the handle 110with a new orientation relative to the chassis 200.

Those skilled in the art will readily recognize that the number ofdiscrete rotational positions available to the handle 110 corresponds tothe number of protrusions 333, 337 and recesses 334, 338. In theillustrated form, the spindle 300 includes three of the protrusions 333,337 and three of the recesses 334, 338 to thereby provide the handle 110with three discretely selectable orientations. Should a first excessivetorque be applied to rotate the handle 110 to a non-desired orientation,a second excessive torque may be applied to return the handle 110 to thedesired orientation in discrete increments. These discrete orientationsare in contrast to certain conventional slip clutches, which provide thehandle with a continuous range of positions when excessive torque isapplied. As a result of the continuous range of positions, it may bedifficult to return the handle to the precise desired orientation afterthe application of an excessive torque. As such, the discrete rotationalpositions provided by the illustrated spindle may be advantageous incomparison to traditional slip clutches.

In certain circumstances, it may be desirable to adjust the thresholdtorque to which the clutch mechanism 330 is configured to limit torquetransmission between the input member 310 and the output member 320. Aswill be appreciated, this threshold torque value depends upon a numberof factors, including but not limited to the angles of the ramps 332,336, the frictional coefficient of the ramps 332, 336, and the biasingforce exerted by the bias mechanism 350. Of these factors, the mostpractical to adjust after manufacture of the spindle 300 is the biasingforce exerted by the bias mechanism 350. Adjusting this biasing forcemay, for example, be accomplished by tightening or loosening the bolt354 to increase or decrease the preload of the spring 352.

In order to adjust the biasing force generated by the bias mechanism 350(and thus the threshold torque operable to be transmitted by the clutchmechanism 330), the handle 110 may be removed from the spindle 300 andan appropriate tool may be inserted via the open proximal end 318 forengagement with the tool-engaging feature 357. The tool may then berotated in an appropriate direction for adjustment of the biasing force.For example, tightening the bolt 354 may increase the preload of thespring 352 to cause a corresponding increase the biasing force (and thusthe threshold torque), while loosening the bolt 354 may decrease thepreload of the spring 352 to cause a corresponding decrease in thebiasing force (and thus the threshold torque).

With additional reference to FIG. 9 , illustrated therein is atorque-limiting spindle 400 according to certain embodiments. Thespindle 400 is substantially similar to the above-described spindle 300,and similar elements and features are indicated with similar referencecharacters. For example, the spindle 400 includes an input member 410,an output member 420, a clutch mechanism 430, a bias mechanism 450, andone or more stop features 460, which respectively correspond to theabove-described input member 310, output member 320, clutch mechanism330, bias mechanism 350, and stop feature(s) 360. In the interest ofconciseness, the following description of the spindle 400 focusesprimarily on elements and features that are different from thosedescribed above with reference to the spindle 300.

In the illustrated form, the spindle 400 includes an external biasmechanism 470 that supplements or replaces the biasing force of theinternal bias mechanism 450. The external bias mechanism 470 generallyincludes a collar 472 and a compression spring 476 mounted in the collar472. The collar 472 includes a proximal end wall 473 having an openingthrough which the input member 410 extends, and a circumferentialsidewall 474 extending distally from the end wall 473. A circlip 475 ispositioned at a distal end of the collar 472 and abuts the flange 428 ofthe output member 420. A portion of the input member 410 extends throughthe spring 476, and the spring 476 is sandwiched between the end wall473 and a flange 413 formed on the input member 410, thereby providingan additional biasing force urging the engagement features 431, 435 ofthe clutch mechanism 430 into engagement with one another.

In the illustrated form, the biasing force provided by the external biasmechanism 470 supplements the biasing force provided by the internalbias mechanism 450, thereby increasing the threshold torque associatedwith the spindle 400. While the illustrated spindle 400 includes boththe internal bias mechanism 450 and the external bias mechanism 470, itis also contemplated that the external bias mechanism 470 may be usedinstead of the internal bias mechanism 450 such that the internal biasmechanism 450 may be omitted. In such forms, the biasing force urgingthe engagement features 431, 435 of the clutch mechanism 430 intoengagement with one another may be defined by the external biasmechanism 470

With additional reference to FIG. 9 , illustrated therein is atorque-limiting spindle 500 according to certain embodiments. Thespindle 500 is substantially similar to the above-described spindle 300,and similar elements and features are indicated with similar referencecharacters. For example, the spindle 500 includes an input member 510,an output member 520, a clutch mechanism 530, a bias mechanism 550, andone or more stop features 560, which respectively correspond to theabove-described input member 310, output member 320, clutch mechanism330, bias mechanism 350, and stop feature(s) 360. In the interest ofconciseness, the following description of the spindle 500 focusesprimarily on elements and features that are different from thosedescribed above with reference to the spindle 300.

In the illustrated form, the spindle 500 includes an external biasmechanism 570 that supplements or replaces the biasing force of theinternal bias mechanism 550. The external bias mechanism 570 generallyincludes at least one first magnet 571 mounted to the input member 510and at least one second magnet 572 mounted to the output member 520. Themagnets 571, 572 are oriented to provide an attractive magnetic forceurging the input member 510 and the output member 520 into engagementwith one another, thereby urging the engagement features 531, 535 of theclutch mechanism 530 into engagement with one another.

In the illustrated form, the biasing force provided by the external biasmechanism 570 supplements the biasing force provided by the internalbias mechanism 550, thereby increasing the threshold torque associatedwith the spindle 500. While the illustrated spindle 500 includes boththe internal bias mechanism 550 and the external bias mechanism 570, itis also contemplated that the external bias mechanism 570 may be usedinstead of the internal bias mechanism 550 such that the internal biasmechanism 550 may be omitted. In such forms, the biasing force urgingthe engagement features 531, 535 of the clutch mechanism 530 intoengagement with one another may be defined by the external biasmechanism 570.

One differentiating feature associated with the magnetic external biasmechanism 570 relates to the feel of the spindle 500 during use. As willbe appreciated by those skilled in the art, the bias force provided bymagnets varies non-linearly with respect to distance, and decreases asdistance increases. Thus, the bias force provided by the magneticexternal bias mechanism 570 will decrease as the engagement features531, 535 drive the magnets 571, 572 away from each other. This featureprovides for a more sudden breakaway when excessive torque is appliedwhen compared to the gradual slippage that occurs in association withthe linear elastic deformation of springs.

With additional reference to FIGS. 11 and 12 , illustrated therein is atorque-limiting spindle 600 according to certain embodiments. Thespindle 600 generally includes a first spindle portion 610 defining oneof an input member or an output member, a second spindle portion 620defining the other of an input member or an output member, and adeformable collar 630 that selectively rotationally couples the firstspindle portion 610 with the second spindle portion 620.

The first spindle portion 610 defines one of an input member or anoutput member, and generally includes a body portion 612 and at leastone radial lobe 614 extending radially from the body portion 612. In theillustrated embodiment, the at least one radial lobe 614 comprises aplurality of the radial lobes 614. While other geometries arecontemplated, in the illustrated form, the radial lobes 614 have agenerally parabolic shape. In certain embodiments, the first spindleportion 610 may be configured as an input member configured forconnection with the handle 110. In such forms, the body portion 612 maybe sized and shaped for reception in the chamber 113. In otherembodiments, the first spindle portion 610 may be configured as anoutput member configured for connection with the hub 230. In such forms,the body portion 612 may be sized and shaped for reception in the hubopening 233.

The second spindle portion 620 defines the other of an input member oran output member, and generally includes a body portion 622. In certainembodiments, the second spindle portion 620 may be configured as aninput member configured for connection with the handle 110. In suchforms, the body portion 622 may be sized and shaped for reception in thechamber 113. In other embodiments, the second spindle portion 620 may beconfigured as an output member configured for connection with the hub230. In such forms, the body portion 622 may be sized and shaped forreception in the hub opening 233.

The collar 630 is coupled with the second spindle portion 620, forexample via a pin 632, and includes a plurality of recessed portions 634that receive the radial lobes 614 of the first spindle portion 610.While other geometries are contemplated, in the illustrated form, therecessed portions 634 have generally semi-circular shapes. The collar630 is formed of an elastically deformable material that resistsrotation of the first spindle portion 610 without preventing suchrotation. In certain embodiments, one or more of the recessed portions634 may comprise a slit 635 that facilitates the elastic deformation ofthe collar 630 during relative rotation of the first spindle portion 610and the second spindle portion 620.

During operation of the spindle 600, the collar 630 initially receivesthe lobes 614 of the first spindle portion 610. When a torque below thethreshold torque is applied between the first spindle portion 610 andthe second spindle portion 620, the collar 630 retains its shape andtransmits such torque between the first spindle portion 610 and thesecond spindle portion 620. When the applied torque exceeds thethreshold torque, the lobes 614 elastically deform the collar 630 topermit relative rotation of the first spindle portion 610 and the secondspindle portion 620. When the first spindle portion 610 is rotatedthrough a predetermined angle relative to the second spindle portion620, the collar 630 returns to its original shape as each lobe 614enters a new recess 634 to provide the handle 110 with a new orientationrelative to the chassis 200. This new orientation is provided in one ofa plurality of discrete orientations, with the number of availablediscrete orientations corresponding to the number of lobes 614 and/orrecesses 634. The handle 110 may be returned to its desired orientationby applying excessive torque to once again cause elastic deformation ofthe collar 630 to return each lobe 614 to its original recess 634.

In the illustrated embodiment, the distal end of the first spindleportion 610 and the proximal end of the second spindle portion 620 aresubstantially flat, and thus do not define an axial clutch mechanismalong the lines of the clutch mechanism 330. It is also contemplatedthat the spindle 600 may be provided with ramps that define an axialclutch mechanism along the lines of the above-described clutch mechanism330. In such forms, the spindle 600 may further include a bias mechanismalong the lines of the bias mechanism 350 such that the rotationalclutch mechanism defined by the deformable collar 630 and the axialclutch mechanism both contribute to the threshold torque.

In certain embodiments, a torque-limiting spindle such as one of theabove-described spindles 300, 400, 500, 600 may be provided to thelockset 100 at the time of manufacture and/or sale to an end user. It isalso contemplated that a torque-limiting spindle may be provided in aretrofit kit for an existing lockset. For example, the lockset 100 mayinitially be provided with a conventional spindle such that locking ofthe hub 220 prevents rotation of the handle attached to the conventionalspindle. A method of retrofitting such a lockset may comprise providinga torque-limiting spindle (e.g., one of the above-described spindles300, 400, 500, 600), wherein the torque-limiting spindle is configuredto replace the existing spindle of the lockset. The method may furthercomprise replacing the conventional spindle with the torque-limitingspindle, thereby converting the existing lockset to a retrofittedlockset along the lines of the above-described lockset 100. Whereas theoriginal lockset (including the conventional spindle) was configured torotationally lock the handle when the lockset was in the locked state,the retrofitted lockset (including the torque-limiting spindle) isoperable to provide a breakaway function whereby the handle is capableof rotating when the lockset is in the locked state.

As noted above, although the illustrated lockset 100 is provided in theform of a mortise lockset, it is also contemplated that atorque-limiting spindle along the lines of the illustrated spindles 300,400, 500, 600 may be utilized in connection with other forms oflocksets. For example, in embodiments in which the spindle is configuredfor use with a cylindrical lockset, the output member may be configuredfor connection with a rotatable member in the form of a portion of a keycam assembly, such as the shell thereof. In embodiments in which thespindle is configured for use with a tubular lockset, the output memberthereof may be configured for connection with a rotatable member in theform of a retractor of a tubular latch mechanism. It is alsocontemplated that other embodiments of the torque-limiting spindledescribed herein may include additional or alternative featuresappropriate for use with the components typical of other locksetformats.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiments have been shown and described and thatall changes and modifications that come within the spirit of theinventions are desired to be protected.

It should be understood that while the use of words such as preferable,preferably, preferred or more preferred utilized in the descriptionabove indicate that the feature so described may be more desirable, itnonetheless may not be necessary and embodiments lacking the same may becontemplated as within the scope of the invention, the scope beingdefined by the claims that follow. In reading the claims, it is intendedthat when words such as “a,” “an,” “at least one,” or “at least oneportion” are used there is no intention to limit the claim to only oneitem unless specifically stated to the contrary in the claim. When thelanguage “at least a portion” and/or “a portion” is used the item caninclude a portion and/or the entire item unless specifically stated tothe contrary.

What is claimed is:
 1. A torque-limiting spindle, comprising: an inputmember extending along a longitudinal axis and configured for connectionwith a handle, the input member comprising an input member end faceincluding a first engagement feature; an output member extending alongthe longitudinal axis and configured for connection with a rotatablemember of a lockset, the output member comprising an output member endface including a second engagement feature; a clutch mechanismcomprising the first engagement feature and the second engagementfeature; and a bias mechanism engaged with the input member and theoutput member and exerting a biasing force urging the first engagementfeature and the second engagement feature into engagement with oneanother, wherein the bias mechanism comprises: a bolt comprising a firstend portion, a head, and an elongated body extending between the firstend portion and the head; and a spring extending along the elongatedbody and engaged with the head such that the spring exerts the biasingforce onto the head to bias the input member toward the output memberand urge the first engagement feature into engagement with the secondengagement feature.
 2. The torque-limiting spindle of claim 1, whereinthe clutch mechanism is operable to transmit a first torque below athreshold torque value between the input member and the output member;and wherein engagement between the first engagement feature and thesecond engagement feature drives the input member and the output memberlongitudinally away from one another in response to application of asecond torque above the threshold torque value such that the clutchmechanism is inoperable to transmit the second torque between the inputmember and the output member.
 3. The torque-limiting spindle of claim 1,wherein the first end portion is a distal end portion coupled with theoutput member; and wherein the head is a proximal head received in theinput member.
 4. The torque-limiting spindle of claim 3, wherein thedistal end portion of the bolt is threadedly engaged with the outputmember; and wherein the proximal head includes a tool-engaging featureconfigured to engage a tool operable to rotate the bolt to therebyadjust a preload of the spring.
 5. The torque-limiting spindle of claim1, wherein the input member comprises an opening configured to receive atool operable to engage a portion of the bias mechanism to adjust abiasing force generated by the bias mechanism.
 6. The torque-limitingspindle of claim 5, wherein the input member further comprises a stopfeature formed adjacent the opening and configured to retain the biasmechanism within the input member.
 7. The torque-limiting spindle ofclaim 1, further comprising an external bias mechanism positionedexternally of the input member and the output member and providing asupplemental biasing force urging the first engagement feature and thesecond engagement feature into engagement with one another.
 8. Thetorque-limiting spindle of claim 7, wherein the external bias mechanismcomprises a collar engaged with the output member and a spring engagedbetween a flange of the input member and an end wall of the collar. 9.The torque-limiting spindle of claim 7, wherein the external biasmechanism comprises a first magnet mounted to the input member and asecond magnet mounted to the output member; and wherein the first magnetand the second magnet are oriented to generate an attractive magneticforce between the first magnet and the second magnet.
 10. Thetorque-limiting spindle of claim 1, wherein the input member is a firstsingle-piece structure that defines the first engagement feature; andwherein the output member is a second single-piece structure thatdefines the second engagement feature.
 11. A lockset comprising thetorque-limiting spindle of claim 1, further comprising: a bolt memberhaving an extended position and a retracted position; a rotatable memberoperably connected with the bolt member such that rotation of therotatable member drives the bolt member between the extended positionand the retracted position, wherein the rotatable member is rotationallycoupled with the output member; and a handle rotationally coupled withthe input member.
 12. A torque-limiting spindle, comprising: an inputmember extending along a longitudinal axis and configured for connectionwith a handle, the input member defining a chamber having an openproximal end, wherein the chamber is defined in part by a distalshoulder; an output member positioned distally of the input member andconfigured for connection with a rotatable portion of a lockset, theoutput member comprising a threaded bore; a bias mechanism mounted atleast partially in the chamber, the bias mechanism comprising: a boltincluding a proximal head and a distal threaded portion, wherein theproximal head is received in the chamber and the distal threaded portionis threadedly engaged with the threaded bore; and a spring mounted tothe bolt between the proximal head and the distal shoulder; wherein thebolt includes a tool-engaging feature configured to engage a tooloperable to rotate the bolt to thereby adjust a preload of the spring;and a clutch mechanism operable to transmit a first torque between theinput member and the output member and inoperable to transmit a secondtorque between the input member and the output member, wherein theclutch mechanism comprises a first engagement feature defined at an endface of the input member, and a second engagement feature defined at anend face of the output member, and wherein the first engagement featureand the second engagement feature are axially pressed into engagementwith one another by the bias mechanism; wherein the first torque is lessthan a threshold torque; wherein the second torque is greater than thethreshold torque; and wherein the threshold torque corresponds to thepreload of the spring.
 13. The torque-limiting spindle of claim 12,wherein the input member has an open proximal end configured to receiveinsertion of the tool.
 14. The torque-limiting spindle of claim 13,further comprising a stop feature formed in the input member, the stopfeature configured to prevent exiting of the bias mechanism via the openproximal end.
 15. The torque-limiting spindle of claim 14, wherein thestop feature comprises a deformation of the input member that projectsradially inward into the open proximal end.
 16. The torque-limitingspindle of claim 12, wherein the clutch mechanism comprises: a firstramp defined by the end face of the input member; and a second rampdefined by the end face of the output member; and wherein the first rampfaces and engages the second ramp such that relative rotation of theinput member and the output member longitudinally drives the inputmember and the output member away from one another.
 17. Thetorque-limiting spindle of claim 12, wherein the clutch mechanismcomprises: a first plurality of ramps defined by the end face of theinput member, the first plurality of ramps defining a first projectionand a first recess; and a second plurality of ramps defined by the endface of the output member, the second plurality of ramps defining asecond projection and a second recess; wherein the first plurality oframps face and engage the second plurality of ramps; wherein the firstprojection is received in the second recess; wherein the secondprojection is received in the first recess; and wherein relativerotation of the input member and the output member longitudinally drivesthe input member and the output member away from one another.
 18. Alockset comprising the torque-limiting spindle of claim 12, furthercomprising: a bolt member having an extended position and a retractedposition; a rotatable member operably connected with the bolt membersuch that rotation of the rotatable member drives the bolt memberbetween the extended position and the retracted position, wherein therotatable member is rotationally coupled with the output member; and ahandle rotationally coupled with the input member.
 19. A torque-limitingspindle, comprising: an input member extending along a longitudinal axisand configured for connection with a handle, the input member comprisingan input member end face; an output member extending along thelongitudinal axis and configured for connection with a rotatable memberof a lockset, the output member comprising an output member end facethat faces the input member end face; a clutch comprising a firstengagement feature associated with the input member end face, and asecond engagement feature associated with the output member end face; anelongate member engaged between the input member and the output memberand comprising a first end portion, and an elongated body extendingbetween the first end portion and the second end portion; and a springextending along the elongated body and exerting a biasing force onto theelongated body to bias the input member toward the output member andurge the first engagement feature into engagement with the secondengagement feature.
 20. The torque-limiting spindle of claim 19, whereinthe clutch is operable to transmit a first torque between the inputmember and the output member and inoperable to transmit a second torquebetween the input member and the output member.
 21. The torque-limitingspindle of claim 20, wherein the first torque is less than a thresholdtorque; wherein the second torque is greater than the threshold torque;and wherein the threshold torque corresponds to a preload force of thespring.
 22. The torque-limiting spindle of claim 19, wherein the clutchis operable to transmit a first torque below a threshold torque valuebetween the input member and the output member; and wherein engagementbetween the first engagement feature and the second engagement featuredrives the input member and the output member longitudinally away fromone another in response to application of a second torque above thethreshold torque value such that the clutch mechanism is inoperable totransmit the second torque between the input member and the outputmember.
 23. The torque-limiting spindle of claim 19, wherein the inputmember is a first single-piece structure that defines the firstengagement feature; and wherein the output member is a secondsingle-piece structure that defines the second engagement feature.